The present invention relates to a display device, and more particularly to a technology that can be effectively applied to a liquid-crystal-panel drive circuit configuration in a liquid crystal display device incorporating plural display elements which receive higher frequency video signals.
In recent years, liquid crystal display devices have been rapidly increased in popularity of their use ranging from small display devices to display terminals such as office automation equipment. Basically, the liquid crystal display device is so configured to form a liquid crystal panel (also referred to as a liquid display element or a liquid crystal cell) which has a layer of liquid crystal composition (a liquid crystal layer) sandwiched between a pair of insulating substrates, at least one substrate of which is made of a transparent glass plate or a transparent plastic substrate.
The liquid crystal panel produces an image by selectively applying voltages to various pixel-forming electrodes, and thereby changing orientation of liquid crystal molecules of the liquid crystal composition in desired pixels. Among the liquid crystal panels, a type is known in which pixels are arranged in a matrix configuration to form a display section. Liquid crystal panels having the matrix configuration of pixels can be classified into two major types; a simple matrix type and an active matrix type. The simple matrix type forms pixels at intersections of two crossing strip electrodes which are respectively disposed on a pair of insulating substrates. On the other hand, the active matrix type has a pixel electrode and an active elements (for example, a thin-film transistor) for pixel selection in each pixel, and by selecting some of the active elements, it forms an image by pixel electrodes coupled to the selected active elements and a reference electrode facing the pixel electrodes.
An active matrix type liquid crystal display device employing an active element (for example, a thin film transistor) for each pixel and switching the active elements is widely used for a display device for notebook personal computers, etc. In general, the active matrix type liquid crystal display device adopts a so-called vertical electric field type which applies an electric field between two electrodes disposed on two substrates, respectively, to change the orientation of liquid crystal molecules in the liquid crystal layer. Also, a so-called horizontal electric field type (also referred to as an In-Plane Switching (IPS) type) has been put in practical use which applies electric fields in the liquid crystal layer such that the direction of the electric fields is approximately parallel with the substrate surface.
On the other hand, a liquid crystal projector has been in practical use which incorporates a liquid crystal display device. The liquid crystal projector irradiates illuminating light from a light source onto a liquid crystal panel and projects an image of the liquid crystal panel onto a screen. Types of liquid crystal panels employed for a liquid crystal projector include the reflective and transmissive types, and when the reflective type is used for the liquid crystal panel, the approximately entire area of a pixel can be used as a usable reflective surface, and therefore the reflective type is more advantageous than the transmissive type for the realization of small-sized, high-definition and high-luminance liquid crystal panels. In addition, among the active matrix type liquid crystal display devices, the driver-circuit-integrated liquid crystal display device is known in which a driver circuit for driving pixel electrodes is disposed on a substrate having the pixel electrodes formed thereon.
Furthermore, among the driver-circuit-integrated liquid crystal display devices, a reflective type liquid crystal display device (hereinafter sometimes referred to as Liquid Crystal on Silicon (LCOS)) is known in which pixel electrodes and a driver circuit are formed on a semiconductor substrate, but not on an insulating substrate.
In addition, in a method of driving the driver-circuit-integrated liquid crystal display device, a drive method is known in which external video signals are supplied in analog form to the liquid crystal display device, and the video signals are sampled by the drive circuit to be supplied to the liquid crystal panel.
In this case, in general, a method is employed in which video signals associated with three color primaries red (R), green (G), and blue (B), respectively, are generated on a single circuit substrate since they are processed by a common LSI, and then are distributed to respective liquid crystal display devices.